Process for the lubrication of surfaces which are exposed to a high temperature



Patented Dec. 11, 1934 UNITED STATES PATENT OFFICE PROCESS FOR THELUBRICATION OF SUR- FACES WHICH ARE EXPOSED TO HIGH TEMPERATURE NoDrawing.

Application September 18, 1929,

Serial No. 393,581

3 Claims.

This invention concerns a process for the lubrication, of hot movingsurfaces as for example, bearings which are exposed to hightemperatures.

Bearings which are exposed to high temperatures occur, for instance, inrolling mills used in the manufacture of iron plates and the like. Thelubrication of these hearings, which some times may attain temperaturesof 300 to 400 0., or even higher, offers great difficulties. As isknown, the lubricants which are ordinarily used, such as mineral oils,vegetable oils, fats and the like, cannot exert a suificient lubricatingaction atthese high temperatures. Therefore, other lubricants have beenproposed which are able to form lubricating films at these temperatures.Such substances are, for instance, the residue of distillation ofmineral oils, such as asphalt. The application of these materials,however, offers many difilculties mainly due to the high viscosity ofthese products at normal temperatures, resulting in the impossibility ofconveying these lubricants to the parts to be lubricated, in theordinary way. It has been attempted to avoid these difliculties byadding so-called flux to the asphalt, but then another difflcultyarises, namely: the danger of the lubricant taking fire from the hightemperature of the bearings, which temperature is generally higher thanthe flash point of the flux. Another method has been attemptedconsisting in conveying the lubricant at an elevated temperature so asto assure viscosity which is sufiiciently low to permit the use ofdevices ordinarily used when applying lubricants of -a low viscosity.

This invention avoids the difficulties by the use of a lubricantconsisting of bituminous material such as asphalt, in an emulsifiedcondition. The asphalt, the properties of which must be chosen inaccordance with the circumstances at the place to be lubricated, formsthe dispersed phase of the emulsion while the dispersing phase of theemulsion comprises water. The preparation of the emulsions may takeplace in any known manner. So, for instance, the emulsion can be made bymixing the asphalt containing a small amount of an acid soluble thereinsuch as napthenic acid, sulphonic acid, oleic acid, or the like, withthe aqueous phase containing a suitable concentration of an alkalinesubstance such as NaOH, KOH, Na2CO3, or the like. Again, the asphalt canbe emulsified in the dispersing phase containing a suitable amount of anemulsifier or stabilizer such as soap, albumin, clay, or the like, withthe help of a colloid mill or other convenient form of emulsifyingapparatus. The so obtained emulsion may be further stabilized in anyknown manner in order to impart the required stability against storage,transport, freezing and the like, by the addition of a suitable amountof astabilizer such as albumins, saponin, casein, tannin, and the like.

In the use of theemulsion for lubricating hot bearings of the typeindicated, the emulsion can be fed continuously to the bearings from aconvenient storage tank. This provides, an advantageous operatingcondition over the present practice wherein hot asphalt is used for thispurpose, in which case it is generally necessary for the operator todaub the bearings from time to time with a hand operation. With the useof the emulsion, the obvious difiiculties attendant upon theaforedescribed hand operation are eliminated, since any suitable feedmechanism adopted for continuously feeding as by gravity-or pumping, astream of emulsion to the bearings may be employed.

Upon reaching the bearings, the water contained in the emulsion, beingin the continuous phase, evaporates rather quickly and almostinstantaneously, in as much as the temperature of the bearings is ashigh as 300 to 400 C. and the bearings themselves are generally of anopen type construction permitting evolution of the steam formed from thewater. In any event, however, the presence of the water does notinterfere with the lubricating value of the asphalt contained in thedispersed phase of the emulsion, and in fact,

the presence of the water is advantageous due to the additional coolingeifect of the water. Upon the evaporation of water, however, there isleft in the bearing asphalt in molten condition, forming a lubricatingfilm around the bearing in much the same manner as when using hotasphalt as such, but without the difliculties that normally prevail inthe application of hot asphalt to the bearings.

The emulsion used may comprise 20 to or asphalt in the dispersed phase,the actual concentration of asphalt, however, being governed by thetemperature of the bearings and the viscosity of the emulsion, whichmust be low enough to permit an even and continuous feed thereof to thebearings. When it is required to realize a considerable cooling effectfrom the water of the emulsion, the latter may be more dilute, that isto say, it should contain less asphalt in proportion to the watercontent thereof.

The use of asphalt in aqueous emulsified condition presents anadditional advantage in that the lubricating effect may be substantiallyincreased by combining with the prepared emulsion, or with the waterprior to emulsification, or in some instances, with the asphalt prior toemulsification, subsaances such as graphite in finely divided form. Ifthis be attempted when using hot asphalt as a lubricant, the viscosityof the molten asphalt is further increased by the graphite, thus furtherincreasing the difiiculties in handling, whereas in accordance with theinvention, any increase in viscosity of the emulsion due to introductionof graphite or the like, may be readily compensated by reducing theviscosity with additional quantities of water, or by a further beatingaction.

I claim as my invention:

1. The process of lubricating surfaces exposed to high temperaturescomprisingv applying to said surfaces an aqueous dispersion of highlyviscous bitumen.

2. The process of lubricating surfaces exposed to high temperaturescomprising applying to said surfaces an aqueous dispersionof asphalt.

3.' The process'of lubricating surfaces exposed to high temperaturescomprising applying to said surfaces an aqueous dispersion of asphaltcontaining a finely divided solid lubricant.

MORITZ JOSEPH HEITMANN.

